Pickling acid is drawn from the tank by means of a chemical pump and fed through a Pre-filter to remove gross particles The acid solution then enters the Interchanger where the temperature is reduced by chilled acid traveling counter-currently through the interchanger (returning from the end of the process). Digital temperature indicators display the temperatures of the solution entering and exiting the Interchanger. The pre-chilled spent acid then enters the Reactor where the acid is blended with the chilled acids circulating through the process. Our new design features an external chilling loop that uses a centrifugal pump to force the spent acid through a specially designed carbon graphite heat exchanger and return the superchilled solution to the reactor. The pump maintains a violent and thorough agitation to minimize formation of crystals on the surface of the exchanger.

A controlled portion of the returning superchilled spent acid solution is diverted to the Crystal Settler. This slurry of superchilled acid and crystals is directed through a thickening tube that sends the crystals to the conical section of the vessel while the clarate (solution without iron crystals) rises to the top of the tank. The overflow port allows the clarate to return to the pump back station where it is pumped through the Interchanger and back to the pickling tank as recovered acid.

The chilled acid is heated by the hot acid coming in from the process tank and uses its own thermal energy to cool the hot acid coming in. In this manner up to 400,000 B.T.U.s can be utilized in each direction, significantly reducing the operating cost of the system and the cost of re-heating the process acid.

The crystals are gravity fed through the bottom of the Crystal Settler and pumped to a gravity filter or Centrifuge (depending upon system size.) These devices separate the solution from the crystal and yield a mostly dry product. The centrate (solution with iron crystals) being discharged by the gravity filter or Centrifuge is returned to the conical Crystal Settler for further growth.

The system is equipped with an automatic backwash that is activated when the system is shut down. This prevents crystals from forming as the exchangers cool during shut down. A microprocessor based control panel is the heart of the process. The system is highly automated to minimize the need for an operator or even much routine maintenance beyond moving dry crystals and changing filters. Highly corrosion resistant and reliable signal generators are employed throughout the system to feed back information for system response. Automated valves, adjusting liquid and crystal movement throughout the system, respond to the programmed signals generated by the microprocessor. The system is also equipped with alarm lights and a buzzer that refuses to be ignored. Digital temperature controllers track the system's thermal efficiency and indicate potential problem sources.

 

Footprint and Elevated Views of Systems
(Low Temperature Design)

small system, footprint	small system, elevated	mid-size system, footprint	mid-system, elevated
large system, footprint	large system, elevated

Components:  Sulfuric Acid Recovery System
(Low Temperature Design)

	Small Systems	Mid-Size Systems	Large Systems
Capacity (liters/day) Capacity (gallons/day)	3,500 - 7,500 1,000 - 2,000	15,000 - 50,000 4,000 - 13,000	75,000 - 150,000 20,000 - 40,000
Primary heat exchanger	optional	optional	optional
External exchanger	carbon-graphite	carbon-graphite	carbon-graphite
Pump station	single pre-filter	single pre-filter	dual pre-filter
Process circulation pump	centrifugal	centrifugal	centrifugal
Automatic backwash process	includes autovalves and check valves	includes autovalves and check valves	includes autovalves and check valves
Crystal reactor	fiberglass, torispherical heads	fiberglass, torispherical heads	fiberglass, torispherical heads
Crystal settler	dual laminate FRP	dual laminate FRP	dual laminate FRP
Crystal separator	gravity filter	centrifuge	centrifuge
Pump back station	tank with sonic level control	tank with sonic level control	tank with sonic level control
Microprocessor based control	A/B Panelview	A/B Panelview	A/B Panelview
Components for automation	non-invasive	non-invasive	non-invasive
Framework & fasteners	epoxy steel	epoxy steel	epoxy steel
Air-cooled chiller	yes	yes	yes
Dimensions and Weights (approximate)
Length	10' (3 m)	17' (5 m)	37' (11 m)
Width	3' (0.9 m)	12' (3.7 m)	13' (3.9 m)
height	19' (5.8 m)	18.5' (5.6 m)	varies by installation
Weight	2 MT	2 MT	varies by installation

last updated May, 2005